Science prints letters blasting methodology and conclusions of study that linked logging to reduced forest regrowth
By Melissa Lee Phillips
Seven months after Science published a controversial paper by Oregon State University (OSU) researchers that claimed the current U.S. policy ofpost-wildfire logging can hinder forest regeneration, the journal is publishing two criticisms of that study. Thefirst, written by forestry scientists from OSU, the federal government, and a consulting company, challenges the study’s context and conclusions, while the second calls into question some of the methodology and statistical tests that the researchers used.
The study’s authors, however defend their research in an accompanying response. “We think the exchange was a useful one to have, but their comments contained no data or compelling evidence that refute our findings,” first author DanDonato, a masters student in forest science at OSU, told The Scientist.
In January, Donato and his colleagues reported that salvage logging after the 2002 Biscuit Fire in Oregon reduced regneration of conifer seedlings. They also reported that logged areas contained excess flammable materials that could provide fuel for new fires.
The current issue of Science includes a now-peer-reviewed letter by the same group, in which they argue Donato’s paper failed to consider several key issues that could influence their results and interpretations, and present citations that help contradict the study. For example, the paper didn’t present information about the management plans implemented after the fire, Newton said. “The logging plans could have been laid out so that the seedlings would not have been damaged,” he told The Scientist.
Also, the study did not take into account the lengthy period of time that passed between the fire and the beginning of logging, Newton said. “Had the salvage logging taken place before the seeds had germinated, the seedlings would not have been injured,” he said. “But it was delayed for three years by legal action.”
Newton and his colleagues also write that the Donato study should have dealt with environmental factors like weather and competing vegetation, which can vary across locales and years. “The things that were left out of the Donato paper are important,” said Newton. “The review process normally would pick those up.”
Two of authors listed with Newton are employees of the U.S. Department of Agriculture (USDA) forest service, while another is retired from the USDA. Newton and another co-author participated in a reforestation program that worked with the government, which has expanded post-fire logging in Oregon. The remaining four authors list no affiliation with the U.S. government.
Donato and his colleagues respond that management instructions and delays in logging may influence seedling regeneration and that further studies should address these issues. But they also cite other work showing that prompt logging in different circumstances also reduced seedling densities.
Applicability across differing situations is “always an issue with ecological studies,” Donato said, and “it’s explicitly stated that the scope of our study is the Biscuit fire salvage.” However, he added, other studies have reported similar findings in different locations. “That’s one thing that’s sort of been baffling about why these results are such a big deal,” he said. “This fits into a larger body of research; it’s really not a stand-alone thing.”
According to Jerry Franklin of the University of Washington in Seattle, who was not involved in the research or the criticisms, Newton et al’s critique “really didn’t address the scientific issues. There were a number of issues having to do with context,” Franklin said, but “I don’t think they really detract from the conclusions that Donato and his associates reached.”
Donato and his colleagues also responded well to a second critique by U.S. Representative Brian Baird (D-WA), according to Franklin. Baird, who has a PhD in clinical psychology, took issue with some of the study design and statistical methods used in the original paper.
“There are always different ways that you can do statistical analysis on these sorts of things,” Franklin said, but “you come out with the same general conclusion no matter which one you use.” Baird, however, claimed that some of Donato’s results would not reach statistical significance if a different analysis were applied.
The disagreement among the researchers may stem from different dogmas about what’s important following a forest fire, Franklin said. Historically, most forestry scientists have focused on getting burned areas back into wood production, Franklin told The Scientist. “They really haven’t carefully examined salvage and reforestation… from the standpoint of ecological values.”
Links within this article
D.C. Donato et al., “Post-wildfire logging hinders regeneration and increases fire risk,” Science, January 20, 2006. PM_ID: 16400111